Optical couplers are frequently used to transfer signals from one circuit to another circuit where it is desirable to electrically isolate the circuits. For example, optical couplers may be used to transmit signals between circuits with widely disparate voltage levels while maintaining the desired electrical isolation between the circuits.
Optical couplers typically include a light emitter (source) and light detector (receiver) without electrical connections between the emitter and detector. The light emitted may be at infrared or visible wavelengths. The receiver is usually selected to substantially match the operating wavelengths of the emitter. After the light emitter receives an input signal from its associated circuit, the emitter will produce a light signal corresponding to the input signal. The light signal is received in some form by the detector and converted into an output signal which is supplied to the circuit associated with the detector. Thus, the input and output signals may be considered coupled between the respective circuits associated with the emitter and the detector.